Method for manufacturing a self-aligned, notched trailing shield for perpendicular recording

ABSTRACT

A perpendicular magnetic write head having a notched, self aligned trailing shield for canting a magnetic field emitted therefrom.

RELATED APPLICATIONS

The present Application is a Divisional Application of commonly assignedpatent application Ser. No. 10/789,563 entitled SELF-ALIGNED, NOTCHEDTRAILING SHIELD FOR PERPENDICULAR RECORDING, filed Feb. 27, 2004, nowU.S. Pat. No. 7,265,941.

FIELD OF THE INVENTION

The present invention relates to perpendicular magnetic recording, andmore particularly to the manufacture of a magnetic write head forperpendicular recording having a self aligned trailing shield.

BACKGROUND OF THE INVENTION

At the heart of a computer is a magnetic disk drive that includes amagnetic disk, a slider where a magnetic head assembly including writeand read heads is mounted, a suspension arm, and an actuator arm. Whenthe magnetic disk rotates, air adjacent to the disk surface moves withit. This allows the slider to fly on an extremely thin cushion of air,generally referred to as an air bearing. When the slider flies on theair bearing, the actuator arm swings the suspension arm to place themagnetic head assembly over selected circular tracks on the rotatingmagnetic disk, where signal fields are written and read by the write andread heads, respectively. The write and read heads are connected toprocessing circuitry that operates according to a computer program toimplement write and read functions.

Typically magnetic disk drives have been longitudinal magnetic recordingsystems, wherein magnetic data is recorded as magnetic transitionsformed longitudinally on a disk surface. The surface of the disk ismagnetized in a direction along a track of data and then switched to theopposite direction, both directions being parallel with the surface ofthe disk and parallel with the direction of the data track. Data densityrequirements are fast approaching the paramagnetic limit wherein thebits of data become so small that they will not remain magnetized.

One means for overcoming this paramagnetic limit has been to introduceperpendicular recording. In a perpendicular recording system, bits ofdata are recorded magnetically perpendicular to the plane of the surfaceof the disk. The magnetic disk may have a relatively high coercivitymaterial at its surface and a relatively low coercivity material justbeneath the surface. A write pole having a small cross section and highflux emits a relatively strong, concentrated magnetic fieldperpendicular to the surface of the disk. This magnetic field emittedfrom the write pole is sufficiently strong to overcome the highcoercivity of the surface material and magnetize it in a directionperpendicular to its surface. This flux then flows through therelatively soft underlayer and returns to the surface of the disk at alocation adjacent a return pole of the write element. The return pole ofthe write element has a cross section that is much larger than that ofthe write pole so that the flux through the disk at the location of thereturn pole (as well as the resulting magnetic field between the diskand return pole) is sufficiently spread out to render the flux too weekto overcome the coercivity of the disk surface material. In this way,the magnetization imparted by the write pole is not erased by the returnpole.

It will be appreciated by those skilled in the art that the highcoercivity of the disk surface material can make it difficult tomagnetize. It has been found that angling the magnetic field slightlycan improve transition sharpness and achieve better media signal tonoise ratio. A proposal to achieve this has been to place a trailingshield near the write gap and magnetically connected with the returnpole. The shield would in effect attract field emitted from the writepole, thereby angling it slightly. A challenge encountered with thisapproach is that some field is lost to the shield, and increasing writefield to compensate for this can lead to adjacent track interference dueto stay fields. Fields fringing out the sides of the write pole, to thewider trailing shield only exacerbate this problem. In addition,shadowing effects from the shield create manufacturing problems duringthe ion milling operation that is generally used to construct desiredflared write pole.

Therefore, there remains a need for a mechanism for canting the magneticfield of a perpendicular write pole, while minimizing field loss andstray field writing. In addition such a mechanism for canting the fieldmust be manufacturable, not creating problems for other criticalmanufacturing steps.

SUMMARY OF THE INVENTION

The present invention provides a method for manufacturing aperpendicular magnetic write head having a notched trailing shield thatminimizes stray fields formation while improving field gradient. Thewrite head having a notched trailing shield is extremely manufacturable,being aligned with the write pole of the perpendicular write head andusing presently existing manufacturing methods.

A write head according to an embodiment of the present invention can beconstructed by first forming a write pole layer as a full film layer,and then depositing a write gap. A shield pedestal portion can then beformed over the write gap material in a desired pattern. An ion millingoperation can then be performed, using the shield pedestal portion as amask for forming the write head. The ion milling process removes writegap material and write pole material in areas not covered by the shieldpedestal portion, resulting in a write pole that is perfectly alignedwith the shield pedestal portion.

A further portion of the shield can then be formed and stitched to areturn pole. This further portion of the shield thickness in the throatheight direction (ie. perpendicular to the ABS) that is much smallerthan that of the initially formed first shield pedestal piece. Thisfurther shield portion can then be used as a mask to define a throatheight thickness of the shield pedestal, the throat height of the shieldpedestal being much smaller than the throat height of the write head.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of thisinvention, as well as the preferred mode of use, reference should bemade to the following detailed description read in conjunction with theaccompanying drawings.

FIG. 1 is a schematic illustration of a magnetic data storage system;

FIG. 2 is a view taken from line 2-2 of FIG. 1, showing a plan view of awrite head;

FIG. 3 is a view taken from line 3-3 of FIG. 3 showing a cross sectionof a magnetic head;

FIG. 4 is an ABS view taken from line 4-4 of FIG. 3; and

FIGS. 5-11 are cross sectional views depicting a magnetic head invarious stages of manufacture.

BEST MODE FOR CARRYING OUT THE INVENTION

The following description is the best embodiment presently contemplatedfor carrying out this invention. This description is made for thepurpose of illustrating the general principles of this invention and isnot meant to limit the inventive concepts claimed herein.

Referring now to FIG. 1, there is shown a disk drive 100 embodying thisinvention. As shown in FIG. 1, at least one rotatable magnetic disk 112is supported on a spindle 114 and rotated by a disk drive motor 118. Themagnetic recording on each disk is in the form of an annular pattern ofconcentric data tracks (not shown) on the magnetic disk 112.

At least one slider 113 is positioned near the magnetic disk 112, eachslider 113 supporting one or more magnetic head assemblies 121. As themagnetic disk rotates, the slider 113 is moved radially in and out overthe disk surface 122 so that the magnetic head assembly 121 may accessdifferent tracks of the magnetic disk where desired data are written.Each slider 113 is attached to an actuator arm 119 by way of asuspension 115. The suspension 115 provides a slight spring force whichbiases slider 113 against the disk surface 122. Each actuator arm 119 isattached to an actuator means 127. The actuator means 127 as shown inFIG. 1 may be a voice coil motor (VCM). The VCM comprises a coil movablewithin a fixed magnetic field, the direction and speed of the coilmovements being controlled by the motor current signals supplied bycontroller 129.

During operation of the disk storage system, the rotation of themagnetic disk 112 generates an air bearing between the slider 113 andthe disk surface 122 which exerts an upward force or lift on the slider.The air bearing thus counter-balances the slight spring force ofsuspension 115 and supports the slider 113 off and slightly above thedisk surface by a small, substantially constant spacing during normaloperation.

The various components of the disk storage system are controlled inoperation by control signals generated by control unit 129, such asaccess control signals and internal clock signals. Typically, thecontrol unit 129 comprises logic control circuits, storage means and amicroprocessor. The control unit 129 generates control signals tocontrol various system operations such as drive motor control signals online 123 and head position and seek control signals on line 128. Thecontrol signals on line 128 provide the desired current profiles tooptimally move and position slider 113 to the desired data track on disk112. Write and read signals are communicated to and from write and readheads 121 by way of recording channel 125.

The above description of a typical magnetic disk storage system, and theaccompanying illustration of FIG. 1 are for representation purposesonly. It should be apparent that disk storage systems may contain alarge number of disks and actuators, and each actuator may support anumber of sliders.

With reference now to FIG. 2, a plan view of an exemplary write element202, can be seen in relation to a slider 113. A coil 204, passingthrough a magnetic yoke 206, induces a magnetic flux in the yoke 206.The magnetic flux in the yoke 206, in turn causes a magnetic field tofringe out at the pole tip 208. It is this fringing field 210 thatwrites magnetic signals onto a nearby magnetic medium.

FIGS. 3 and 4 illustrate a cross section of the magnetic head assembly121, including a read element 302 sandwiched between first and secondshields 304, 306 and a write element 202. The write element 202 isseparated from the read element 302 by a dielectric layer 308. The headassembly has an air bearing surface ABS 324 which is the surface that isheld in proximity to the surface of the disk 112 during operation.

The write element 202 includes a shaping layer 312 constructed of amagnetic material such as NiFe, which can be deposited byelectroplating. The shaping layer 312 can be formed to stop short of theABS surface 324. A write pole sub-layer 313 is formed on top of theshaping layer 312, and is formed with a taper 314 at a pole tip region316 which is near the ABS surface. A non-magnetic material such asAlumina Al₂O₃ 318 can be used to fill the pole tip region 316 adjacentto the taper 314.

A write pole 320 is magnetically connected with the write pole sub-layer313. The write pole 320 is preferably formed of laminated layers of ahigh magnetic saturation material (high Bsat) such as CoFe, NiFe ortheir alloys with interspersed non-magnetic film such as Ct, Ru, etc.With reference to FIG. 4, the write pole is formed with a trapezoidalshape. As those skilled in the art will appreciate, the trapezoidalshape of the write pole 320 prevents adjacent track writing when thehead 121 experiences skew on while flying over the disk 112 (FIG. 1). Awrite gap material layer 322, is formed over the write pole 320, fromthe ABS surface 324 to a back gap 326. The write gap material is a nonmagnetic material which can be either a dielectric material such asalumina or a conductive material such a metal. The back up is formed ofa magnetic material such as NiFe and extends from the write polesublayer 313 to a return pole 328. The write pole 320, comprises a poletip region 321, a flare region 323 and a yoke region 327.

An electrically conductive coil 332 passes between the write gap layer322 and return pole 328 and is electrically insulated by an insulationlayer 334, which can be for example alumina or hard baked photoresist.The coil 332 may or may not be insulated from the write gap layer 322,depending upon design requirements and the material that makes up thewrite gap layer 322.

With continued reference to FIGS. 3 and 4, a magnetic trailing shield338 extends from the return pole 328 toward the write pole 320. Themagnetic shield 338 is constructed with a main shield portion 340 and anotched shield pedestal 342. The main shield portion 340 is magneticallyconnected with the return pole 328, and is relatively wide as can beseen with reference to FIG. 4. The notched shield portion 342 is muchnarrower than the main shield portion 340, having the same width as poletip portion 321 of the write pole 320, and is laterally aligned with thewrite pole 314 as can be seen with reference to FIG. 4. The distancebetween the laterally opposed sides 341, 343 of the notched shieldportion 342 defines a track width TW of the notched shield portion 342and write pole 320. As can be seen with reference to FIG. 3, the mainshield portion 340 and notched shield pedestal portion have the samedepth in a direction perpendicular to the ABS, which defines a commonthroat height TH for the notched shield portion 340 and main shieldportion 342 and are in fact self aligned, as will be explained ingreater detail below.

In another embodiment of the present invention, the trailing shield 338could be constructed as one or more pieces having the same width as thewrite pole 320, and having that width completely to the return pole 328.

As electrical current flows through the coil 322, a magnetic flux isinduced through a yoke formed of the return pole 328, back gap 326,write pole sublayer 313, shaping layer 312 and write pole 320. Due tothe arrangement of the write pole 320, write pole sublayer 313 andshaping layer 312, the magnetic flux is advantageously stronglyconcentrated at the tip of the write pole 320, and causes a concentratedmagnetic field to emit from the write pole 320 toward the disk 112. Thepresence of the shield 338 causes the emitted, concentrated field to becanted a desired amount.

Optimally, the distance from the write pole 320 to the shield notchedportion 342 of the shield 338 should be about half of the distance fromthe ABS to the soft under layer 344 of the disk 112. It should beappreciated that the Figures presented herein are not to scale, and forpurposes of clarity some elements may be shown larger relative to otherelements than they would actually be, or appear further away from orcloser to other elements than they would actually be.

As the write gap thickness is reduced, flux from the write pole isshared between the soft underlayer 344 of the media 112 and the shield338. This design improves write field gradient at the expense of writeflux. To minimize write flux lost to the shield and still achieve theangling effect of the effective field, as a rule of thumb, the shieldthickness as measured from the ABS 324 should be less than the trackwidth of the write element, (ie. less than the width of the write pole320 as viewed from the ABS) and is more preferably approximately equalto half the trackwidth. As the write pole 320 is scaled toward tighterdimension and constrained by the design for skew, the amount of writefield coming out at the write pole tip is attenuated and insufficient todrive the head. One approach to alleviate this is to drive the head withhigher write current, but this would lead to adjacent track interferenceand protrusion due to heat generation. Notching the trailing shield 338as described above alleviates this cross track interference. Experimentshave shown that an 8-10 percent increase in effective write field can beachieved if a portion of the trailing shield 338 is notched and alignedto the write pole 320. The challenge in fabricating such an aligned,notched trailing shield in a write element having a trailing shieldsingle pole design is the ability to tightly control the gap 322 betweenthe write pole and the shield 338 and self-aligning the notched shieldportion 342 to the write pole since the critical dimensions of the writepole trackwidth are in the nanometer scale. For example, in an 88nanometer trackwidth write pole, the width of the notched portion 342 ofthe trailing shield would have to be 88 nanometers.

FIGS. 5-7 illustrate a method of fabricating a perpendicular write headhaving a self aligned notched trailing shield. The shaping layer 312,constructed of a magnetic material such as NiFe is formed over asubstrate 501, such as alumina, and can be deposited for example bysputtering and electroplating. As can be seen with reference to FIG. 5,the shaping layer is constructed so as to be recessed from the ABS plane324. The write pole sublayer 313 is then constructed over the shapinglayer 312, and is formed with the taper 314. A non-magnetic materialsuch as alumina 316 fills the area adjacent to the shaping layer 312 andtaper 314 in the pole tip region 316, near the ABS 324.

With reference now to FIGS. 6 and 7 a full film of high magneticsaturation (high Bsat) material 602 is deposited. The high magneticsaturation material is preferably a laminated material. Laminatedmaterials have been found to have improved lower magnetic switchingfields when compared with single layer, solid films. A thin layer ofwrite gap material 604 is then deposited on top of the high Bsatmaterial. Thereafter, a magnetic shield pedestal 606 is formed over thewrite gap material. The shield pedestal 606 is constructed of a magneticmaterial such as NiFe and can be formed by lithographic patterning andplating, using techniques familiar to those skilled in the art, and atthis point in the manufacturing process extends back to the back gap andhas the same shape as the desired final shape of the write pole 320. Thelines 608, 610 denote the transitions between pole the pole tip region321, flare region 323, and yoke region 327, and are not meant to imply adiscontinuity in the pedestal material. With reference now to FIG. 7 anion mill 702 is performed, which removes portions of the write gapmaterial layer 604 and magnetic layer 602 that are not covered by theshield pedestal, resulting a structure illustrated with reference toFIG. 8. With reference to FIG. 9, angled and sweep milling operations902 can be performed to form the desired trapezoidal shape of the writepole 314.

With reference to FIG. 10, a the main shield portion 340 (formed furtherfrom the write pole) is formed above the shield pedestal 320, having alateral width parallel with the ABS surface that is much wider than thepedestal 320, and having a short throat height dimension (perpendicularto the ABS surface). With reference to FIG. 11, an ion milling processis then performed, using the main shield 340 portion as a mask to definethe throat height of the shield pedestal 320, thereby self aligning theshield pedestal with the main shield portion in the throat heightdirection. The detection of write gap material in the ion millatmosphere indicates that ion milling should be terminated.

It will be appreciated that the method described above forms a perfectlyaligned notched shield by using the notched pedestal portion 342 of theshield 338 (FIG. 3) as a mask for forming the write pole 320, and usingthe main shield portion 340 as a mask for the pedestal 320. Since theshield pedestal 342 protects the write gap 342 during subsequent ionmilling operations, the critical gap thickness can be accuratelycontrolled and maintained.

With reference again to FIGS. 3 and 4, with the shield pedestal 342formed, the remaining elements can be constructed. The insulator 330 isdeposited, which can optionally be followed by a chemical mechanicalpolishing process. Insulation 336 can be deposited and the back gap 326formed according to methods familiar to those skilled in the art. Inaddition, the main portion 340 of the shield 338 can be constructed. Asmentioned above, constructing the shield 338 as two separate layers isonly one possible embodiment. The shield, 338 could also be constructedby extending the shield pedestal 342 completely to the return pole 328,so that the pedestal 342 constitutes the shield 338. The return pole 328can be constructed by electroplating.

In an optional method for further defining the dimensions of the shieldpedestal 342, the main portion 340 of the shield 338 can be used as amask to define the throat height of the pedestal 342. The throat heightis the length of the pedestal in the dimension perpendicular to the ABS324.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Other embodiment will no doubt occur to those skilled in theart. For example, the read element could either be formed above or belowthe write element and if formed below the write element, a heat sinklayer, such as Cu could be included to conduct heat away from the writehead to protect the read element. Thus, the breadth and scope of apreferred embodiment should not be limited to any of the above-describedexemplary embodiments, but should be defined only in accordance with thefollowing claims and their equivalents.

1. A method for constructing a write head for perpendicular magneticrecording, comprising: depositing a layer of write pole material;depositing a non-magnetic write gap material over said write polematerial; forming a magnetic shield pedestal over said write gapmaterial layer, said shield pedestal having first and second lateralsides defining planes perpendicular to an air bearing surface; andperforming a material removal process to remove selected portions ofsaid write gap layer and said write pole material using said shieldpedestal as a mask to prevent removal of said write gap material andsaid write pole material disposed beneath said shield pedestal; whereina distance between said first and second lateral sides of said shieldpedestal defines a track width and wherein said shield pedestal has adepth in a direction perpendicular to said air bearing surface that isless than said track width.
 2. A method as in claim 1 wherein saidmaterial removal process comprises ion milling.
 3. A method as in claim1 wherein said material removal process comprises ion milling at anangle between 0 and 90 degrees with respect to at least one of saidlateral side walls of said shield pedestal.
 4. A method for constructinga write head for perpendicular magnetic recording, comprising:depositing a layer of write pole material; depositing a non-magneticwrite gap material over said write pole material; forming a magneticshield pedestal over said write gap material layer, said shield pedestalhaving first and second lateral sides defining planes perpendicular toan air bearing surface; and performing a material removal process toremove selected portions of said write gap layer and said write polematerial using said shield pedestal as a mask to prevent removal of saidwrite gap material and said write pole material disposed beneath saidshield pedestal; wherein said shield pedestal is constructed of alaminated magnetic layers.
 5. A method for constructing a write head forperpendicular magnetic recording, comprising: depositing a layer ofwrite pole material; depositing a non-magnetic write gap material oversaid write pole material; forming a magnetic shield pedestal over saidwrite gap material layer, said shield pedestal having first and secondlateral sides defining planes perpendicular to an air bearing surface;performing a material removal process to remove selected portions ofsaid write gap layer and said write pole material using said shieldpedestal as a mask to prevent removal of said write gap material andsaid write pole material disposed beneath said shield pedestal; anddepositing a magnetic main shield portion over said shield pedestal; andperforming a second material removal process, using said magnetic mainshield material as a mask to remove selected portions of said shieldpedestal to define a throat height of said shield pedestal, said throatheight being a dimension measured from said air bearing surface.
 6. Amethod as in claim 5, wherein said second material removal processcomprises ion milling.